Professor Peter Piot was one of the co-discoverers of the Ebola virus during its first outbreak in Zaire, in 1976. Photograph: Leon Neal/AFP/Getty Images

Peter Piot was one of the scientists who discovered the Ebola virus in what is now the Democratic Republic of the Congo (DRC) in 1976, but as he watched the latest outbreak develop in west Africa this summer, he began to think with alarm of the early years of Aids.

“The worst possible fears were confirmed in June or July that this was very different from ’76,” he said. “Context is extremely important. There had been civil war, a lack of trust, breakdown of health services because of civil war and dictatorship in Guinea. Most professionals had left the country. In Liberia there were 51 registered medical doctors and four of those worked for the ministry of health, so 47 for a population of 4.5 million. These are countries in reconstruction after civil war, still very fragile politically and with traditional beliefs in the causation of disease – it’s not pathogens but witchcraft.

“But all that exists in DRC. The main difference, I think, has been denial and the lack of response. It reminds me of the beginning of Aids.” The same attitude prevailed, he said. “Just – no, it is not us, it does not exist. Precious time was wasted.”

Past outbreaks have been halted through prompt action to trace every contact of anyone who falls ill. Isolation and quarantine are medieval techniques, said Piot, byin comparison with modern medicine, but they have stopped about 25 small outbreaks since that first one. This time the response was too slow. As with Aids, there was denial. In March, when the first official lab confirmation of Ebola in Guinea was made, others beside Médecins sans Frontières (which has done a heroic job, according to Piot) should have reacted. “But WHO was silent. Governments denied it. All that meant that it got out of control.”

Piot understands the parallel with Aids better than most. He helped set up the UN agency on HIV, called UNAIDS, and ran it as executive director from its launch in 1996 until he left in 2008. Under his leadership, UNAIDS became the driving force of the global response to the HIV epidemic.

By June, Piot was getting alarmed. He had heard MSF’s warnings, to which the World Health Organisation had not paid attention. Ebola outbreaks begin in rural areas, when one person gets infected by handling or eating a forest creature, probably a fruit bat, with the virus. But by the summer there was a case in Conakry, Guinea’s crowded capital city, where infection could spread so much more rapidly, along with cases in Liberia and Sierra Leone. Acting as much on gut instinct as evidence, said Piot, he gave an interview to CNN on 2 July. “I said this is out of control and then I surprised myself and said we need a quasi-military operation,” he said. “Afterwards I thought, oh my God, what did I say? I’m Flemish by culture. We don’t exaggerate. We use understatement if anything. But unfortunately I was right.”

After that he got very frustrated, he said, asking why the WHO and the US were not doing more. “MSF can’t carry the weight of a nationwide response in three countries,” he said. “It may also be because of my Aids background. I always felt if we had acted much earlier and had the resources we have now for HIV, it wouldn’t have got out of hand.”

In 1996, antiretroviral drugs became available for people with HIV, but it took about 10 years before they were on the agenda for Africa. “It became a bit of an obsession for me to bring down the price. It took a good five years before the money was coming in. So the way I look at it is very coloured by my Aids experience.”

There are parallels too in the stigma. People who have survived Ebola and those who nurse them are rejected by frightened friends and family, just as occurred with Aids.

The UK, he said, the old colonial power in Sierra Leone, had done well in what is now a humanitarian crisis. There had been major investment by the UK in ending the civil war, he said, and now: “I’m really impressed by the UK response. It is co-ordinated. It’s kind of a textbook example of how to do things, with the NGOs and the government and some scientific underpinning.

“But I also feel we need to be realistic about what we can do from the outside. Constructing beds, providing care, logistics, ambulances and what have you. But the key element is going to be stopping transmission in the community. With a bunch of white doctors who don’t speak the local language and don’t know about local customs, I don’t see how that can happen.”

The most likely scenario now, he thinks, is a decreasing number of new infections in quite a few locations as people avoid contact with the sick, but it will be patchy. “It’s always mind-blowing to think the whole epidemic started with one person,” he said. “HIV was probably the same – from one person to 70 million.

“If it can come from one person, it can always be reignited or refuelled by another person. So without a vaccine, it may not be possible to control it.”

Earlier in the epidemic, the Centers for Disease Control in the United States outlined a worst-case scenario involving 1.4m Ebola cases in Sierra Leone and Liberia by mid-January. Those numbers “didn’t pass the laughter test”, he said and have fortunately proved very pessimistic. According to the WHO, there had been more than 18,600 reported cases by 17 December. The true figures may be even double that, but nowhere near the CDC projection. There have been about 7,000 deaths and each is a tragedy, but in terms of global health mortality, that is small numbers. “More women have died from giving birth and more from malaria,” said Piot. “But Ebola is like Sars [severe acute respiratory syndrome]. Health workers die and it destabilises countries.”

Three vaccine candidates will go into trials in January in the region, but it cannot be assumed the solution will be quick or easy. There is a lot of suspicion of western medicine. Stories on social media in Sierra Leone tell of a US conspiracy to introduce the virus, further fuelled by the arrival of American troops in Liberia to fight the disease. “We need to do a lot of preparatory work and explain things. We need to talk to traditional leaders. There are very powerful secret societies in Sierra Leone and Guinea,” he said.

Piot is opposed to testing drugs against a placebo, which is the gold standard way to find out if they work. “We went through that with Aids, which is why I’m so against it,” he said. When death is likely, nobody should be denied a drug that might help.

When it is all over – whenever that is – the world needs to think hard about how to prevent such a health disaster happening again. “I think we need a postmortem: how we as an international community responded, and not only the WHO,” he said.

Member nations, including the US and UK, approved the WHO’s cuts to its capacity to respond to a disease outbreak. He said the international community must not miss the chance to bolster that response capability. “One thing is for sure – we will have other epidemics. Certainly pandemic flu is going to come at some time,” he said. The WHO was accused of over-reacting to swine flu, but “I think it is better to over-react than under-react.”